1. Field of the Invention
The invention relates to a suspension system attaching a powerplant to an aircraft frame, whether laterally to the fuselage or suspended from the wing.
2. Related Art
More specifically the present invention relates to a suspension system wherein a bearing is mounted on a bearing cage affixed to a powerplant housing. The bearing is slidable on a spindle that has an axis that is perpendicular to the powerplant axis and is mounted on a spindle support solidly joined to the airframe. Two lateral linkrods each link the housing and one of two suspension arms supported by the spindle support.
Loads along the longitudinal axis are absorbed by the spindle. When the powerplant is mounted laterally to the fuselage, the spindle also absorbs vertical loads along the vertical or Z-axis, whereas the linkrods absorb the lateral loads along the Y-axis. If the powerplant is suspended underneath the wing, the spindle also absorbs the lateral loads along the Y-axis, whereas the vertical loads are absorbed by the linkrods. In both assembly modes, the torque due to engine rotation is absorbed by the bearing and the linkrods.
When the powerplant operates under certain flight conditions, in particular at takeoff, the spindle and the linkrods are subjected to considerable loads. To prevent the powerplant from becoming disengaged, engine aircraft manufacturers must either oversize the suspension components or reinforce certain elements in order to create a double load absorption path. Further, engine aircraft manufacturers must also include additional standby linkrods that will become active in case the spindle or a linkrod breaks. All these solutions entail a substantial increase in weight, and in some instances, an increase in the number of parts.
The objective of the present invention is to create a suspension system for a powerplant mounted on an aircraft frame which is fitted with safety features that are integrated in the region of the bearing, without increasing weight or adding substantially more parts.
Another objective of the invention is to create an engine suspension system that easily integrates safety features and which requires only minor modification of the suspension""s components.
Such objectives are met by the present invention using a suspension system comprising a spindle that is inserted into a cylindrical, slidable bearing that is concentric to the spindle and slidably arranged within a recess formed by two suspension arms and a spindle support that are attached to the aircraft frame. The bearing is supported by a bearing cage that is connected to the powerplant housing, and the two suspension arms are connected to the powerplant housing by two lateral linkrods. The spindle support is concentric with the spindle""s axis to limit the travel of the bearing cage in a plane perpendicular to the spindle axis in the event a spindle breaks.
Advantageously, the spindle is arranged so as to prevent the bearing from leaving contact in the event of a linkrod fracture. In one embodiment, the spindle comprises a radial shoulder located at one end that is substantially perpendicular to the spindle axis and spaced apart from a portion of the bearing cage during suspension. In the case of a linkrod fracture, the spindle supports the bearing cage by the shoulder coming into contact with a portion of the bearing cage.
In a second embodiment of the invention, the bearing cage is connected to the housing by means of screws that have axes that run parallel to the spindle axis. The screws are fitted with shank segments that pass through orifices in a small collar formed on the spindle support. The heads of the screws are located by a distance J2 from the outside of the flange and have a diameter larger than that of the orifices. The screw head constitutes the first stop, whereas the flange constitutes the second stop.